This application is based upon and claims priority of Japanese Patent Application No.2002-006406, filed on Jan. 15, 2002, the contents being incorporated herein by reference.
(1) Field of the Invention
The present invention relates to semiconductor devices and portable terminal equipment, and more particularly, to a semiconductor device that realizes power reduction in such a manner that a supply of power to part of the internal circuit is periodically turned on and off in a standby mode in which no communication takes place, such as a baseband LSI (Large-Scale Integration) in W-CDMA (Wideband Code Division Multiple Access), and portable terminal equipment using such a semiconductor device.
(2) Description of the Related Art
Recently, the LSI fabrication process has improved the minimum feature length, and has realized a transistor having a gate of 0.10 xcexcm is close at hand. Miniaturization increases integration of mounting transistors, while requiring reduction in the threshold voltage that defines LSI operation. This would result in increase in leakage current that flows through transistors in standby mode. That is, a large current flows only by power on even when the circuit is not in the active mode. This is an essential problem. Battery-driven portable terminal equipment, such as a cellular phone, is required to keep the internal circuit in standby mode. Increase in leakage current would bring about various practical problems such as shortening of the continuous talk time and standby time.
FIG. 9 is a flowchart of an intermittent receiving in the W-CDMA communication system, and FIG. 10 is a timing chart of control timing in the intermittent receiving.
Terminal equipment is called by a base station in the W-CDMA communication system as follows.
In standby mode, a supply of power to hardware MHW and its processor (DSP: Digital Signal Processor) in a modem part of the equipment as well as hardware CHW and its processor CDSP in a channel codec part is periodically turned off (sleep mode) and on (sleep-released mode) every two seconds, for example, every 1.2 seconds, and intermittent receive takes place as long as power is on.
When intermittent receive starts from the sleep mode of the terminal equipment (step S1), a supply of power to the modem part and the channel codec part is turned on (step S2), and the processor CDSP of the channel codec part start the boot process (step S3). Next, the modem part receives a signal over PICH (paging Indicator Channel) (step S4). The PICH is a channel for transferring a call indicator sent for notification of a call received at any of portable terminal equipment in a base station in which the location has been registered (in-group incoming call). The modem determines whether there is an in-group incoming call (step S5). The hardware CHW and its processor CDSP in the channel codec part are notified of the determination result.
If it is determined that there is no in-group incoming call, the modem part is switched to the sleep mode, and the hardware CHW and its processor CDSP in the channel codec part are switched to the sleep mode (steps S6 and S7). In contrast, it is determined that there is an in-group incoming call, the modem part receives the paging channel PCH immediately (about two seconds) soon thereafter (step S8), and determines if the in-group incoming call is directed to its own portable equipment by checking the paging channel PCH. The hardware CHW stores data of the paging channel PCH (step S9). The processor CDSP of the channel codec part sets a decode parameter (step S10) after it is determined there is an in-group incoming call. The hardware CHW of the channel codec part decodes the paging channel PCH by using the decode parameter set by the processor CDSP (Step S1).
As described above, the paging indicator channel PICH is a physical channel that can simply be determined only by demodulating (de-spreading and decision), while the paging channel PCH has been bit-interleaved and has been processed in error correction, needing a particular decoding process therefor.
In receive check processing, the paging indicator channel PICH is intermittently decoded (every 1.2 seconds) in modes other than the talk mode (in standby mode). A supply of power to the conventional baseband LSI is off (sleep status) during the time other than the intermittent receive. In contrast, power is supplied with all the circuits of the LST during the intermittent receive irrespective of whether there is a call.
However, complexity of the communication sequence in W-CDMA results in an extremely large circuit scale and makes it difficult to reduce power consumption.
In addition, recent improvement in the minimum feature scale would cause a larger leakage current, which is negligible as compared to the operating current and brings about difficulties in power reduction.
In the conventional art, leakage current flows in a circuit that is not originally needed to operate when there is no call in intermittent receive (sleep-released mode). This increases current consumption and shortens the continuous talk time and standby time.
Taking into consideration the above, it is an object of the present invention to provide a semiconductor device that makes unnecessary operation inactive and thus reduce power consumption because of leakage current.
The above object of the present invention is achieved by a semiconductor device having a plurality of blocks that are sequentially processed step by step. The semiconductor device includes power supply systems respectively provided in the plurality of blocks, the power supply systems being divided into a non-controlled power supply group in which power is always on and controlled power supply groups in each of which groups a supply of power can be turned on/off independently, the non-controlled power supply group comprising power system controller for controlling a timing for turning on/off a power supply system of at least one of the controlled power supply groups, each of the controlled power supply groups except a final stage thereof comprising next-processing necessity determining unit for determining whether processing at a next stage is needed on the basis of a result of determination processed in its own controlled power supply group.
The above object of the present invention is also achieved by a portable terminal wherein a supply of power to a block unnecessary for intermittent receive control processing during a time other than intermittent receiving in a standby mode, the portable terminal equipment comprising: timer, belonging to a non-controlled power supply group in which power is always on, for generating a first control signal that turns on a supply of power to a first controlled power supply group including a first block necessary for determination of in-group incoming call and turns off the supply of power during a time other than the intermittent receiving; first power switch for turning on/off a supply of power to the first controlled power supply group in accordance with the first control signal from the timer; incoming call determining unit, belonging to the first controlled power supply group, for generating a second control signal that turns on/off a power supply to a second controlled power supply group including a second block necessary for processing an incoming call on the basis of determination of an in-group incoming call by the first block; and second power switch for turning of/off power supply to the second controlled power supply group in response to the second control signal from the incoming call determining unit.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.